Different safety arrangements are known in the prior art for motor vehicles. These arrangements routinely comprise a winding mechanism for automatically winding a seat belt around a belt reel. The automatic winding action ensures that the applied seat belt rests loosely and comfortably against the passenger's body and when the seat belt is not being used, it is wound up around the belt reel. The seat belt unwinds easily when it is put on, thereby ensuring freedom of movement of the passenger inside the vehicle.
Furthermore, so-called seat belt pretensioners are provided in known safety arrangements. The effect of seat belt pretensioners is to tighten the seat belt in order to pull the passenger against the backrest of the vehicle seat, thereby reducing the risk of injury in the event of a collision between the vehicle and another vehicle or a traffic obstacle. Known seat belt pretensioners can be classified as irreversible or reversible seat belt pretensioners. The irreversible seat belt pretensioner is only activated when an accident has already happened, for example a collision with another vehicle. Crash sensors detect the collision and transmit a corresponding activation signal to the irreversible seat belt pretensioner. Irreversible seat belt pretensioners can only ever be activated or released once, since an accident has definitely occurred. Reversible seat belt pretensioners, on the other hand, are intended to be able to be activated several times, even rapidly in succession, based on signals which indicate the possibility of an imminent crash. In other words, reversible seat belt pretensioners are always intended to be able to be activated when a crash is possible or likely, but has not yet actually taken place or been detected.
In the case of reversible seat belt pretensioners, a critical driving situation is not determined by crash sensors which only determine a crash when it has actually occurred, but by driving dynamics sensors which provide information about the current movement state of the motor vehicle. For example, this includes the determination of the longitudinal, lateral and vertical acceleration of the vehicle. If these measured values exceed a limiting value, then the preventative activation of the reversible seat belt pretensioner takes place. If the measured values fall short of the limiting value again and in fact, there has not been a crash, the reversible seat belt pretensioner is deactivated again so that the seat belt can be returned into its normal position in which the passenger is afforded a greater freedom of movement. It is possible to reactivate the reversible seat belt pretensioner in the next critical driving situation.
DE 199 61 799 B4 describes a seat belt system with a reversible seat belt pretensioner. The known reversible seat belt pretensioner has an electromotive drive which reversibly pretensions the seat belt into a intermediate safety position with a specific tensile force as a function of the probability of an accident situation derived from sensor signals. The critical driving situation which is detected by the precrash sensor technology (not described in more detail) and which leads to activation of the seat belt pretensioner can be, for example skidding, emergency braking etc.
DE 103 45 726 A1 describes a retention system for holding back a passenger in a car. The known retention system has a reversible seat belt pretensioner operated by a control device. The control device is connected to a vehicle situation detection device for dynamically detecting vehicle situation data, for example the lateral acceleration of the vehicle, and is connected to a passenger parameter detection device for dynamically detecting passenger parameter data, for example the weight of the passenger. The seat belt pretensioner is controlled as a function of the determined vehicle situation data and passenger parameter data.
DE 102 30 483 A1 describes a method for activating a two-stage irreversible seat belt pretensioner. In the known method, the longitudinal acceleration of the motor vehicle is detected and subjected to an integration whereby the integral of the acceleration is compared with a tripping threshold. If this tripping threshold is exceeded, the irreversible seat belt pretensioner is activated.
DE 103 32 024 A1 describes a method for activating a reversible seat belt pretensioner for releasing a belt pull-out stop of a retention belt in a motor vehicle, which may be activated by an acceleration sensor. The release time for the belt pull-out stop is established as a time when the detected acceleration falls below an acceleration threshold.
The known methods for controlling a reversible seat belt pretensioner have stood the test of time, but there is no suitable activation of the seat belt pretensioner during dangerous steering manoeuvres, so that passenger safety during dangerous steering manoeuvres is worth improving.
It is therefore an object of the present invention to provide a method for controlling a reversible seat belt pretensioner in a motor vehicle which allows a suitable activation of the seat belt pretensioner during dangerous steering manoeuvres, thereby increasing the safety of the vehicle occupants. A further object of the invention is to provide a safety arrangement comprising a reversible seat belt pretensioner with which it is possible to implement the method according to the invention.